(i) Field of the Invention
The present invention relates to a method for preparing a recording magnetic head for use in a magnetic disc device.
(ii) Description of the Related Art
In recent years, the capacity of a magnetic disc device for use as the external storage device of a computer is being enlarged, and with the enlargement of the capacity, the data recording density of the recording medium of the magnetic disc device is enhanced, and the data transfer speed between the recording medium and a recording magnetic head is increased. Therefore, a magnetic head is demanded which can realize a high-speed magnetic recording.
The magnetic head is usually prepared using a so-called thin film technique, and the magnetic pole of the magnetic head is formed by plating a film of nickel iron (NiFe) alloy by an electric plating process or the like. It is known that a tensile stress is generated as an internal stress in the NiFe alloy film formed by the plating process. Therefore, with the intention of avoiding the disturbance of a magnetic domain structure by the internal stress, it is general to use an alloy of 80% of Ni and 20% of Fe (Ni80Fe20 alloy) as the NiFe alloy to form the magnetic pole, which has only a small magnetostriction and which is not easily susceptible to an influence of internal stress.
For the magnetic head with the magnetic pole formed of the Ni80Fe20 alloy, however, the saturation magnetic flux density of Ni80Fe20 alloy is as small as about 1 T and the specific resistance is also as small as about 20 xcexcxcexa9cm. Therefore, if the recording frequency is large, the recording ability becomes insufficient because of a drop in recording magnetic field intensity caused by the loss of eddy current in the magnetic pole.
Therefore, it is proposed to use the NiFe alloy which has a large specific resistance as well as a large saturation magnetic flux density (high Bs-NiFe alloy), and has a ratio of Ni of 35% to 70%. This high Bs-NiFe alloy is expected to contribute to a high-speed magnetic recording ability because its specific resistance is as large as 20 to 70 xcexcxcexa9cm, and the saturation magnetic flux density is also as large as 1.3 to 1.6 T.
However, since such high Bs-NiFe material provides a positive magnetostriction, and its magnetostriction constant is 1 to 3xc3x9710xe2x88x925, and larger than that of the Ni80Fe20 alloy, the tensile stress remaining inside the plated film tends to deteriorate the magnetic domain structure of the magnetic pole from a closure magnetic domain which is an essentially desirable magnetic domain structure, to the magnetic domain structure to be avoided which is called xe2x80x9clongitudinal magnetic domainxe2x80x9d. This deterioration of the magnetic domain structure results in a lowered recording ability in a high-frequency area, and the problem is that the high potential inherent in the high Bs-NiFe material cannot be derived.
The present invention has been developed in consideration of the above-described circumstances, and an object of the present invention is to provide a method for preparing a magnetic head in which the magnetic head having a high-speed magnetic recording ability can be prepared.
To attain the above-described object, according to the present invention, there is provided a method for preparing a magnetic head comprising:
a coil forming step of forming a conductive layer constituting a coil;
a heat-shrinkable layer forming step of laminating a heat-shrinkable layer consisting of a heat-shrinkable substance after the conductive layer in laminating order;
a magnetic pole layer forming step of laminating a magnetic pole layer consisting of a magnetic body indicating a positive magnetostriction after the heat-shrinkable layer in the laminating order; and
a heat treatment step of heating a laminate constituted by laminating a plurality of layers including the heat-shrinkable layer and the magnetic pole layer to shrink the heat-shrinkable layer.
Here, another magnetic pole layer consisting of another magnetic body other than the magnetic body constituting the above-described magnetic pole layer may be laminated on the above-described magnetic pole layer. Moreover, the magnetic body constituting the above-described magnetic pole layer may be any magnetic body indicating the positive magnetostriction, such as magnetic bodies of an NiFe alloy, an NiFeMo alloy and other alloys obtained by adding various elements to a base of NiFe alloy. Furthermore, examples of the method of forming the magnetic pole layer include an electric plating process, an electroless plating process, a sputtering process and a deposition process.
Additionally, the above-described conductive layer may constitute a single layer coil, or a multilayered coil.
According to the method for preparing the magnetic head of the present invention, since the heat-shrinkable layer shrinks by the heat treatment step, the internal stress of the magnetic pole layer forms a compression stress, and the magnetic domain structure of the magnetic pole layer is improved. As a result, the magnetic head which can realize a high-speed magnetic recording is prepared.
Moreover, since the heat treatment step in the method for preparing the magnetic head of the present invention requires no external magnetic field and the magnetic domain structure is improved even by the heat treatment with no magnetic field, the method for preparing the magnetic head of the present invention can be applied to MR head in which a spin valve is used as a magnetoresistive (MR) effect film.
In the method for preparing the magnetic head of the present invention, the magnetic body constituting the above-described magnetic pole layer is preferably an alloy of nickel and iron in which the ratio of nickel is in a range of 35% to 70% by weight.
Since the NiFe alloy with the ratio of nickel in the range of 35% to 70% by weight indicates a positive magnetostriction and a magnetostriction constant of 1 to 3xc3x9710xe2x88x925, the magnetic domain structure of the magnetic pole layer of the NiFe alloy is securely improved by the heat treatment step.
Moreover, in the method for preparing the magnetic head of the present invention using such alloy, the heat treatment step preferably comprises shrinking the thickness of the heat-shrinkable layer by 1% or more.
More preferably, the heat treatment step comprises shrinking the thickness of the heat-shrinkable layer by 2% or more.
By shrinking the thickness of the heat-shrinkable layer by 1% or more in the heat treatment step, the magnetic domain structure of the magnetic pole layer can securely be improved. Moreover, the anisotropic magnetic field of the magnetic pole layer can be set to be larger than 4 Oe by shrinking the thickness of the heat-shrinkable layer by 2% or more, and natural resonance between the magnetic field and spontaneous magnetization can be prevented from occurring during high-speed magnetic recording.
Moreover, in the method for preparing the magnetic head of the present invention, the above-described heat-shrinkable layer forming step preferably comprises forming an insulating layer of a heat-shrinkable insulating body to cover the conductive layer.
Furthermore, it is preferably that the insulating body is a thermosetting resist, and the above-described heat-shrinkable layer forming step comprises applying the resist to the conductive layer, and heating the applied resist at a predetermined temperature to form a resist insulating layer.
The magnetic head has an insulating layer to cover the conductive layer constituting the coil, and the magnetic pole layer is laminated on the insulating layer. By forming the insulating layer as the heat-shrinkable layer, a complicated magnetic head structure can be avoided. Moreover, the insulating layer to cover the conductive layer is generally formed of the resist, and it is known that the thermosetting resist indicates heat-shrinkable properties. Therefore, the resist insulating layer can be utilized as the heat-shrinkable layer, and the method for preparing the magnetic head of the present invention can easily be realized.
In case that such resist insulating layer is utilized as the heat-shrinkable layer, the above-described heat-shrinkable layer forming step preferably comprises heating the resist at a temperature in a range of 180xc2x0 C. to 300xc2x0 C.
Moreover, the heat treatment step preferably comprises heating the laminate at a temperature in a range of 200xc2x0 C. to 350xc2x0 C.
In case that the resist is heated at a temperature less than 180xc2x0 C. in the heat-shrinkable layer forming step, the resist strength becomes insufficient, and there is a possibility that a crack is generated in a process of preparing a slider or the like. On the other hand, in case that the resist is heated at a temperature higher than 300xc2x0 C. in the heat-shrinkable layer forming step, the shrinkage of the resist insulating layer becomes insufficient in the heat treatment step.
Moreover, in case that the laminate is heated at a temperature less than 200xc2x0 C. in the heat treatment step, the shrinkage of the resist insulating layer becomes insufficient. In case that the laminate is heated at a temperature higher than 350xc2x0 C., there is a high possibility that the magnetic head is damaged.
According to the method for preparing the magnetic head of the present invention, the magnetic head having a high-speed magnetic recording ability can be prepared.